1. Field of the Invention
The present invention relates to a process for providing thermoplastic film tubes with anti-blocking means directly during their production by cooling the film tube in its interior with an aqueous release agent suspension directly after extrusion.
2. Background Information
Film tubes composed of thermoplasts, preferably polyvinylidene chloride (PVDC), have a tendency to block owing to their smooth surfaces. The tubes can therefore be opened only by means of adhesive tape, for example for filling.
Tubes composed of thermoplastics are usually produced in such a way that the thermoplastic material is extruded by means of a tubular die and is subsequently cooled internally and externally in a water bath. A water-oil emulsion is generally used as an internal coolant. Although this emulsion prevents the insides of the tube from sticking together directly after extrusion, it cannot prevent blocking of the final tube. Attempts have therefore been made to overcome this problem by applying an anti-blocking agent to the interior of the finished tube.
According to the teaching of EP No. 0018167, this is achieved in an additional operation in which an anti-blocking agent is supplied to the interior of a moving film tube from a storage container arranged in the interior and dispersed by centrifugal force.
In the past, however, it has not been possible to provide such tubes with anti-blocking agents directly during production.